A photon source includes a photo-pair generator and a detection device. The photo-pair generator is configured to generate a photon-pair in receiving an input signal. A first photon of the photon-pair is output from the photon source via a first optical path. The detection device is configured to receive a second photon of the photon-pair. The detection device includes a transistor that has a semiconducting component that is a source and a drain of the transistor, and a superconducting component that is adjacent to the semiconducting component and is a gate of the transistor. The transistor is configured to transition from an off state to an on state in response a photon being incident upon the detection device.
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1. A photon source, comprising:
a photon-pair generator configured to generate a photon-pair in response to receiving an input signal, wherein a first photon of the photon-pair is output from the photon source via a first optical path; and
a detection device configured to receive a second photon of the photon-pair, the detection device including a transistor, wherein:
the transistor includes a semiconducting component that comprises a source and drain of the transistor and a superconducting component, adjacent to the semiconducting component, that comprises a gate of the transistor; and
the transistor is configured to transition from an off state to an on state in response a photon being incident upon the detection device.
4. The photon source of
the transistor further comprises a current source coupled to the transistor and configured to provide a bias current that is below a current threshold of the superconducting component; and
the superconducting component is configured to, in response to an input current exceeding the current threshold, transition to a non-superconducting state and generate heat sufficient to increase a temperature of the semiconducting component above a semiconducting threshold temperature of the semiconducting component so that the transistor transitions from an off state to an on state in response to the input current exceeding the current threshold.
5. The photon source of
6. The photon source of
7. The photon source of
8. The photon source of
one or more optical waveguides optically coupled the photon-pair generator, the one or more optical waveguides configured to:
transmit the first photon of the photon-pair along the first optical path; and
transmit the second photon of the photon-pair along a second optical path, distinct from the first optical path, toward the detection device.
9. The photon source of
10. The photon source of
the one or more optical waveguides includes a wavelength division multiplexer configured to:
transmit the first photon, having a first wavelength, along the first optical path; and
transmit the second photon, having a second wavelength, along the second optical path.
11. The photon source of
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This application is a continuation of U.S. application Ser. No. 16/046,815, filed Jul. 26, 2018, which claims priority to U.S. Provisional Application No. 62/538,565, filed Jul. 28, 2017, entitled “Superconductor Nanowire Transistor Based On Interlayer Heat Transfer;” U.S. Provisional Application No. 62/578,921, filed Oct. 30, 2017, entitled “Photodetector with Superconductor Nanowire Transistor based on Interlayer Heat Transfer;” and U.S. Provisional Application No. 62/591,600, filed Nov. 28, 2017, entitled “Nanowire Transistor,” each of which is incorporated by reference herein in its entirety.
This application is also related to International (PCT) Patent Application PCT/US18/33041, filed May 16, 2018, entitled “Gated Superconducting Photon Detector;” and U.S. application Ser. No. 16/046,807, filed Jul. 26, 2018, each of which is incorporated by reference herein in its entirety.
This relates generally to transistors, including but not limited to, transistors utilizing semiconducting freeze-out effects.
A transistor is a device used to switch and/or amplify electrical signals. A transistor has at least three terminals for connection to a circuit, sometimes labeled as a gate, a source, and a drain. Transistors are generally configured such that a current or voltage applied to the gate allows current to flow from the source to the drain. However, as device sizes decrease, various technical issues, such as gate oxide leakage current in semiconductor-based transistors, have limited the performance of semiconductor-based transistors.
Superconductors are materials capable of operating in a superconducting state with zero electrical resistance under particular conditions. Additionally, in some circumstances, superconductors generate heat when transitioning from a superconducting state to a non-superconducting state.
There is a need for systems and/or devices with more efficient and effective methods for providing the functionality of a transistor. Such systems, devices, and methods optionally complement or replace conventional systems, devices, and methods for providing the functionality of a transistor.
As an example in accordance with some embodiments, a transistor is composed of a semiconducting wire (e.g., acting as a source and drain of the transistor) and a superconducting wire (e.g., acting as a gate of the transistor). In this example, the superconducting wire is electrically isolated from the semiconducting wire, and the semiconducting wire is initially maintained at a temperature below a critical temperature for current flow through the semiconducting wire (representing an “off” state for the transistor and sometimes referred to as a “freeze-out state”). The superconducting wire in this example is initially in a superconducting state. While in the superconducting state a current is introduced to the superconducting wire that exceeds a critical current for the wire. As a result, the superconducting wire transitions to a non-superconducting state. During the transition, the superconducting wire generates heat sufficient to heat the semiconducting wire above the critical temperature for current flow. The increase in temperature thus allows current flow through the semiconducting wire (representing an “on” state for the transistor). Thus, in these embodiments, the transition of the superconductor wire from the superconducting state to the non-superconducting state switches the transistor from an off state to an on state.
As another example in accordance with some embodiments, a transistor is composed of a semiconducting wire (e.g., acting as a gate of the transistor) and a superconducting wire (e.g., acting as a source and drain of the transistor). In this example, the superconducting wire is electrically isolated from the semiconducting wire, and the semiconducting wire is initially maintained at a temperature below a critical temperature for current flow through the semiconducting wire. The superconducting wire in this example is initially in a superconducting state, representing an “on” state for the transistor. While in the superconducting state, a voltage is introduced to the semiconducting wire. The voltage generates an electromagnetic field that lowers a current threshold for the superconducting wire. As a result, the superconducting wire transitions to a non-superconducting state. In the non-superconducting state, less current flows through the superconducting wire, representing an “off” state for the transistor. Thus, in these embodiments, the application of the voltage to the semiconducting wire switches the transistor from an on state to an off state.
In one aspect, some embodiments include a transistor having: (1) a first wire including a semiconducting component configured to operate in an on state at temperatures above a semiconducting threshold temperature; and (2) a second wire including a superconducting component configured to operate in a superconducting state while: (a) a temperature of the superconducting component is below a superconducting threshold temperature; and (b) a first input current supplied to the superconducting component is below a current threshold; where: (i) the semiconducting component is located adjacent to the superconducting component; (ii) in response to a first input voltage, the semiconducting component is configured to generate an electromagnetic field sufficient to lower the current threshold such that the first input current exceeds the lowered current threshold, thereby transitioning the superconducting component to a non-superconducting state; (iii) the transistor is configured to operate in an on state while the superconducting component is in the superconducting state; and (iv) the transistor is configured to operate in an off state while the superconducting component is in the non-superconducting state.
In another aspect, some embodiments include a method for operating a superconductor-based transistor. The method includes operating the superconductor-based transistor in a first mode, including: (a) maintaining the transistor in an off state, including: (i) maintaining a superconducting component of the transistor in a superconducting state; and (ii) maintaining a semiconducting component of the transistor in an off state; and (b) transitioning the transistor from the off state to an on state, including supplying current to the superconducting component, wherein the current exceeds a superconducting current threshold for the superconducting component; where, in response to the current supplied to the superconducting component, the superconducting component transitions to a non-superconducting state and generates heat sufficient to increase a temperature of the semiconducting component above a semiconducting threshold temperature and allow current flow through the semiconducting component.
In another aspect, some embodiments include a transistor having: (1) a first wire including a semiconducting component configured to operate in an on state at temperatures above a semiconducting threshold temperature; and (2) a second wire located adjacent to the semiconducting component; where: (a) in response to an input current, the second wire is configured to generate heat sufficient to increase a temperature of the semiconducting component above the semiconducting threshold temperature; (b) the transistor is configured to operate in an off state while the semiconducting component is maintained at a temperature below the semiconducting threshold temperature; and (c) the transistor is configured to operate in an on state while the semiconducting component is at a temperature above the semiconducting threshold temperature.
In yet another aspect, some embodiments include a transistor device configured to perform any of the methods described herein.
In yet another aspect, some embodiments include a transistor device, comprising: (1) a superconducting wire, the superconducting wire comprising a first layer of the transistor device; (2) a semiconducting wire, the superconducting wire comprising a second layer of the transistor device and configured to transfer current from a source of the transistor to a drain of the transistor; and (3) an electrically-insulating layer isolating the first layer from the second layer.
In yet another aspect, some embodiments include a method for fabricating a superconductor-based transistor. The method includes: (1) providing a superconducting wire; (2) depositing an electrically insulating layer over the superconducting wire; and (3) forming a semiconducting wire on the electrically insulating layer.
In yet another aspect, some embodiments include a method for fabricating a transistor device, comprising: (1) providing a semiconducting wire; (2) depositing an electrically insulating layer over the semiconducting wire; and (3) forming a superconducting wire on the electrically insulating layer.
Thus, devices and systems are provided with methods for fabricating and operating freeze-out transistors, thereby increasing the effectiveness, efficiency, and user satisfaction with such systems and devices.
For a better understanding of the various described embodiments, reference should be made to the Detailed Description below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures.
Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.
Many modifications and variations of this disclosure can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.
The present disclosure describes transistor devices that utilize a freeze-out property of semiconductors in conjunction with resistive heat generation of superconductors (and other conductors) to achieve transistor functionality. As an example, in accordance with some embodiments, a transistor is composed of a semiconducting wire (e.g., acting as a source and drain of the transistor) and a superconducting wire (e.g., acting as a gate of the transistor). In this example, the superconducting wire is electrically isolated from the semiconducting wire, and the semiconducting wire is initially maintained at a temperature below a critical temperature for current flow through the semiconducting wire (representing an “off” state for the transistor and sometimes referred to as a “freeze-out state”). The superconducting wire in this example is initially in a superconducting state. While in the superconducting state a current is introduced to the superconducting wire that exceeds a critical current for the wire. As a result, the superconducting wire transitions to a non-superconducting state. During the transition, the superconducting wire generates heat sufficient to heat the semiconducting wire above the critical temperature for current flow. The increase in temperature thus allows current flow through the semiconducting wire (representing an “on” state for the transistor). Thus, in these embodiments, the transition of the superconductor wire from the superconducting state to the non-superconducting state switches the transistor from an off state to an on state.
The present disclosure also describes transistor devices that utilize electromagnetic fields generated by semiconductors in conjunction with superconducting to non-superconducting transitions for superconductors to achieve transistor functionality. As another example, in accordance with some embodiments, a transistor is composed of a semiconducting wire (e.g., acting as a gate of the transistor) and a superconducting wire (e.g., acting as a source and drain of the transistor). In this example, the superconducting wire is electrically isolated from the semiconducting wire, and the semiconducting wire is initially maintained at a temperature below a critical temperature for current flow through the semiconducting wire. The superconducting wire in this example is initially in a superconducting state, representing an “on” state for the transistor. While in the superconducting state, a voltage is introduced to the semiconducting wire. The voltage generates an electromagnetic field that lowers a current threshold for the superconducting wire. As a result, the superconducting wire transitions to a non-superconducting state. In the non-superconducting state, less current flows through the superconducting wire, representing an “off” state for the transistor. Thus, in these embodiments, the application of the voltage to the semiconducting wire switches the transistor from an on state to an off state.
As used herein, a “superconducting transistor” or “superconductor-based transistor” is a transistor having one or more superconducting components. As used herein, a “superconducting” material is a material that is capable of operating in a superconducting state (under particular conditions). For example, a superconducting material is a material that operates as a superconductor (e.g., operates with zero electrical resistance) when cooled below a particular temperature (e.g., a critical temperature) and having less than a threshold current flowing through it. A superconducting material is also called herein a superconduction-capable material. The superconducting materials may also operate in an “off” state where little or no current is present. In some embodiments, the superconducting materials operate in a non-superconducting state during which the materials have a non-zero electrical resistance (e.g., a resistance in the range of one thousand to ten thousand ohms). For example, a superconducting material supplied with a current greater than a threshold superconducting current for the superconducting material may transition from a superconducting state with zero electrical resistance to a non-superconducting state with non-zero electrical resistance. As an example, superconducting layer 106 in
As used herein, a semiconducting component is deemed to be in an “on” state when the semiconducting component is at a temperature above a critical temperature of a semiconducting material (e.g., TC 208 in
As used herein, a transistor is deemed to be in an “on” state when a current is allowed to flow from a source of the transistor to a drain of the transistor (e.g., the transistor has a low drain-source resistance), and a transistor is deemed to be in an “off” state when a current flow from the source to the drain is prevented or reduced (e.g., the transistor has a high drain-source resistance).
As used herein, a “wire” is a section of material configured for transferring electrical current. In some embodiments, a wire includes a section of material conditionally capable of transferring electrical current (e.g., a wire made of a superconducting material that is capable of transferring electrical current while the wire is maintained at a temperature below a critical temperature). A cross-section of a wire (e.g., a cross-section that is perpendicular to a length of the wire) optionally has a geometric (e.g., flat or round) shape or an irregular (also sometimes called a non-geometric) shape. In some embodiments, a length of a wire is greater than a width or a thickness of the wire (e.g., the length of a wire is at least 5, 6, 7, 8, 9, or 10 times greater than the width and the thickness of the wire).
As used herein, the term “light intensity” or simply “intensity” refers to the number of photons incident on a unit area, e.g., a superconducting wire, per unit time. The term “intensity” includes a situation where only a single photon is incident on the detector in a given time period and also includes a situation where multiple photons are incident on the detector in the given time period. For example, a first light pulse having a first intensity that is greater than a second light pulse having a second intensity includes a first light pulse that includes more photons than a second light pulse. For example, the first light pulse can include 10 photons or 100 photons, while the second light pulse can include one photon, two photons, . . . , 9 photons, etc.
As shown in
Although
Although
In some embodiments in which the region 306 of the semiconductor 304 has a highest critical temperature, the region 306 may operate as a block preventing current flow through the semiconductor, e.g., when the semiconductor 304 is at a temperature that is higher than respective critical temperatures of regions 305 and 307, but below the critical temperature of region 306. In this example, once the region 306 heats up to its critical temperature, current will flow through the semiconductor 304. In some embodiments, a portion of the superconductor 302 that is proximate to the semiconductor 304 has a constriction (e.g., similar to the constriction 301 shown in
Although
Although
Although
Although some of
In some embodiments, one or more portions of the semiconductor 304 adjacent to the non-superconducting region are maintained above the critical temperature (e.g., TC 208) of the semiconductor 304. In some embodiments, one or more portions of the semiconductor 304 adjacent to the non-superconducting region are doped to lower the critical temperature (e.g., TC 208) of the semiconductor 304 for the one or more portions of the semiconductor 304 (e.g.,
In some embodiments, the non-superconducting region 420 of the superconductor 302 prevents or reduces current flow through the superconductor 302. Once the current 412 is no longer supplied, the non-superconducting region 420 (and the semiconductor 304) cool down over time. Once the temperature of the semiconductor 304 falls below the critical temperature of the semiconductor 304, the current flow through the semiconductor 304 is reduced or blocked (e.g., the semiconductor 304 returns to the “freeze-out” state).
The photodetector also includes semiconductor photodetector 506 (e.g., a photodiode that includes silicon, germanium, indium gallium arsenide, lead sulfide, and/or mercury cadmium telluride). In some embodiments, semiconductor photodetector 506 is voltage-biased (e.g., using an optional voltage source). Semiconductor photodetector 506 is configured to generate photoelectrons upon receiving light. In
In some embodiments, (not shown) the transistor 500 is configured to be a photodetector. For example, the superconducting component 502 of the transistor 500 is coupled to a waveguide so as to detect photons from the waveguide. In some embodiments in which the superconducting component 502 is configured to be a photodetector, the superconducting component 502 is biased so as to operate in a superconducting state in the absence of incident photon(s). In some embodiments, in response to receiving incident photon(s) of a first intensity, photocarriers (also called hot electrons) are generated in the superconductor (e.g., through the breaking of the superconductor's cooper pairs) which, in turn, causes transition of superconducting component 502 from a superconducting state to a non-superconducting state. In some embodiments in which the superconducting component 502 is configured to be a photodetector, the photodetector does not include the semiconductor photodetector 506.
In some embodiments, readout circuit 508 includes one or more superconductor and/or semiconductor components. In some embodiments, readout circuit 508 is configured to transition to a state that indicates whether a resistance of semiconducting component 504 is a logical 0 (e.g., resistance is greater than a predefined resistance threshold) or a logical 1 (e.g., resistance is less than the predefined resistance threshold), and thereby facilitates providing the logical state of the photodetector to other circuits or system components. In some embodiments, readout circuit 508 is configured to measure a current flowing through semiconducting component 504 or a voltage drop over semiconducting component 504. For example, in some embodiments, readout circuit 508 is a voltage readout circuit. In some embodiments, readout circuit 508 includes a resistor (e.g., 50 ohms) and the readout circuit is configured to measure a voltage drop over the resistor. In some embodiments, readout circuit 508 includes a voltage source 511 or a current source 513.
In some embodiments, source 510 provides an electrical signal (e.g., an electrical current) that is used to bias semiconductor photodetector 506 and/or superconducting component 502.
While semiconducting component 504 is in the “off” state, there is a small (or zero) voltage differential over capacitor 522. Conversely, while the semiconducting component 504 is in the “on” state, there is a larger voltage differential over capacitor 522.
While semiconducting component 504 is in the “off” state, there is a small (or zero) voltage differential over capacitor 522 and semiconducting component 504 in the “off” state has a larger voltage differential.
At the first time shown in
The circuit maintains (802) the superconductor-based transistor in an off state at a first time. In some embodiments, the superconducting component is at a temperature below a superconducting threshold temperature (e.g., below TC 206) at the first time. In some embodiments, the semiconducting component is at a temperature below a semiconducting threshold temperature (e.g., below TC 208) at the first time. In some embodiments, the transistor is maintained at temperatures below the superconducting threshold temperature via a cryostat or the like.
In some embodiments, maintaining the superconductor-based transistor in an off state includes maintaining (806) the semiconductor component below a semiconducting threshold temperature (e.g., below TC 208). In some embodiments, maintaining the superconductor-based transistor in an off state includes maintaining (808) the superconducting component below a superconducting threshold temperature (e.g., below TC 206). In some embodiments, maintaining the superconductor-based transistor in an off state includes supplying (810) a current to the superconducting component that is below the superconducting current threshold (e.g., current 412).
In some embodiments, the method 800 includes supplying (e.g., the circuit supplying) a second current to the semiconducting component, such that the second current flows through the semiconducting component while the semiconductor is at a temperature above the semiconducting threshold temperature.
While the superconducting component is operating in a superconducting state and the semiconducting component is in an off state, the circuit initiates (814) transition of the superconductor-based transistor from the off state to an on state by supplying a third current to the superconducting component. In some embodiments, the third current exceeds (816) a superconducting current threshold for the superconducting component.
In some embodiments, in response to the current supplied to the superconducting component, the superconducting component transitions (818) to a non-superconducting state and generates heat sufficient to increase a temperature of the semiconducting component above a semiconducting threshold temperature (e.g., above TC 208) and allow current flow through the semiconducting component (as shown in
In accordance with some embodiments, a method for operating a superconductor-based transistor includes: (1) at a first time, maintaining the superconductor-based transistor in an off state, where the superconductor-based transistor includes a first wire including a semiconducting component (e.g., semiconductor 304) and a second wire including a superconducting component (e.g., superconductor 302); and (2) while (a) the superconducting component is operating in a superconducting state and (b) the semiconducting component is in an off state, initiating transition of the superconductor-based transistor from the off state to an on state by supplying a current to the superconducting component (e.g., current 414), the current exceeding a superconducting current threshold for the superconducting component.
The circuit operates (902) a superconductor-based transistor in a first mode (e.g., illustrated in
The circuit maintains (906) the superconducting component at a temperature below a superconducting temperature. The circuit supplies (908) a current (e.g., current 412,
The circuit transitions (910) the transistor from the off state to an on state, including supplying a second current (e.g., current 414,
In response to the current supplied to the superconducting component, the superconducting component transitions (914) to a non-superconducting state and generates heat sufficient to increase a temperature of the semiconducting component above a semiconducting threshold temperature and allow current flow through the semiconducting component (e.g.,
In some embodiments, the circuit operates (916) the superconductor-based transistor in a second mode (e.g., illustrated in
The circuit maintains (920) the superconducting component in a superconducting state. The circuit supplies (922) a third current (e.g., current 604) to the superconducting component, the third current below a current threshold for the superconducting component. The circuit maintains (924) a semiconducting component of the transistor in an off state.
The circuit transitions (926) the transistor from the on state to an off state (e.g.,
In response to the voltage, the semiconducting component is configured to (928) generate an electromagnetic field (e.g., field 608) sufficient to lower the current threshold such that the first current exceeds the lowered current threshold, thereby transitioning the superconducting component to a non-superconducting state.
In accordance with some embodiments, a method for operating a superconductor-based transistor includes operating the superconductor-based transistor in a first mode (e.g., illustrated in
In some embodiments, maintaining the superconductor-based transistor in the off state includes maintaining the superconducting component at a temperature below a superconducting temperature.
In some embodiments, maintaining the superconductor-based transistor in an off state includes supplying a current (e.g., current 412,
In some embodiments, the method includes operating the superconductor-based transistor in a second mode (e.g., illustrated in
The photodetector includes (1002) a superconductor-based transistor. In some embodiments, the transistor includes: (1) a first wire including a semiconducting component configured to operate in an on state at temperatures above a semiconducting threshold temperature, and (2) a second wire including a superconducting component configured to operate in a superconducting state while: (a) a temperature of the superconducting component is below a superconducting threshold temperature, and (b) an input current supplied to the superconducting component is below a current threshold. In some embodiments, the transistor includes a first wire including a semiconducting component (e.g., semiconducting component 504,
The photodetector initiates (1004) exposure of a superconducting wire electrically coupled to the second wire to light of a first intensity (e.g., shining light on superconducting wire 516,
In some embodiments, the superconducting wire generates a first current based on the light of the first intensity provided to the superconducting wire, and the first current causes the superconducting component to transition from the superconducting state to a non-superconducting state (e.g.,
The photodetector generates (1006) heat (e.g., due to current flowing through the superconducting component while in the non-superconducting state) sufficient to increase the temperature of the semiconducting component above the semiconducting threshold temperature (e.g., semiconducting component 504 transitions into the “on” state,
In some embodiments, the photodetector determines (1010) whether the light of the first intensity has been received by the superconducting wire based on one or more characteristics of an electrical signal flowing through the first wire. For example, when a voltage drop across the semiconducting wire is above a predefined voltage drop threshold, it is deemed that no light above a detection threshold is detected; when the voltage drop across the semiconducting wire is below the predefined voltage drop threshold, it is deemed that light above the detection threshold is detected. In some embodiments, the photodetector measures (1012) the one or more characteristics of the electrical signal flowing through the first wire. In some embodiments, the one or more characteristics include (1014) a current and/or a voltage of the electrical signal flowing through the first wire.
In some embodiments, the photodetector measures (1016) one or more characteristics (e.g., voltage, current, etc.) of an electrical signal flowing through the first wire before the superconducting wire is exposed to the light of the first intensity.
In some embodiments, the photodetector measures (1018) one or more characteristics of an electrical signal flowing through the first wire while the superconducting wire is exposed to the light of the first intensity.
In some embodiments, the photodetector compares (1020) the one or more characteristics of the electrical signal flowing through the first wire measured before the superconducting wire is exposed to the light of the first intensity and the one or more characteristics of the electrical signal flowing through the first wire measured while the superconducting wire is exposed to the light of the first intensity.
In accordance with some embodiments, a method for detecting light is performed with a transistor. The transistor includes a first wire including a semiconducting component (e.g., semiconducting component 504,
In some embodiments, the method also includes determining whether the light of the first intensity has been received by the superconducting wire based on one or more characteristics of an electrical signal flowing through the first wire (e.g., when a voltage drop across the semiconducting wire is above a predefined voltage drop threshold, it is deemed that no light above a detection threshold is detected; when the voltage drop across the semiconducting wire is below the predefined voltage drop threshold, it is deemed that light above the detection threshold is detected).
In some embodiments, the method includes measuring the one or more characteristics (e.g., voltage, current, etc.) of the electrical signal flowing through the first wire.
In some embodiments, the method includes measuring one or more characteristics of an electrical signal flowing through the first wire before the superconducting wire is exposed to the light of the first intensity (e.g., measuring voltage, current, etc. when the superconducting wire is not receiving light); measuring one or more characteristics of an electrical signal flowing through the first wire while the superconducting wire is exposed to the light of the first intensity (e.g., measuring voltage, current, etc. when the superconducting wire is receiving light); and determining whether the light of the first intensity has been received by the superconducting wire by comparing the one or more characteristics (e.g., voltage, current, etc.) of the electrical signal flowing through the first wire measured before the superconducting wire is exposed to the light of the first intensity and the one or more characteristics of the electrical signal flowing through the first wire measured while the superconducting wire is exposed to the light of the first intensity. For example, a reduced voltage drop across the semiconducting component is used to determine that the superconducting wire is receiving light. In some embodiments, the one or more characteristics include a current and/or a voltage of the electrical signal flowing through the first wire.
Turning to
An input optical waveguide 1113 optically couples a pump photon source (not shown) to photon pair generator 1103. A pump photon 1102 enters the pumped photon pair generator 1103 via input optical waveguide 1113. For the sake of illustration, any photons illustrated here are depicted outside of the waveguides, but one of ordinary skill will appreciate that in a physical device, these photons will propagate within one or more guided modes of the waveguide. In some embodiments, the pumped photon pair generator 1103 can include a nonlinear optical material that generates two output photons, referred to as idler photon 1104 and signal photon 1106 from one or more input pump photons 1102. For example, the pumped photon pair generator 1103 can generate a pair of output photons using a process known as spontaneous four wave mixing. The pair of output photons, signal photon 1104 and idler photon 1106, are typically generated having different wavelengths/frequencies, e.g., with the sum of the energies of the signal and idler equal to the energy of the pump photon. After generation, signal photon 1104 and idler photon 1106 are optically coupled to the input of WDM 1105 via waveguide 1108. Because photons 1104 and 1106 have different wavelengths/frequencies, WDM 1105 redirects each photon along a different output waveguide, e.g., signal photon 1104 is directed along the heralding waveguide path 1113 and idler photon 1106 is redirected along the switched output waveguide path 1115. Which photon is directed to which path is not critical and the path of the idler photon and signal photon can be exchanged without departing from the scope of the present disclosure.
In this example, a superconducting photon detector 1107, e.g., a superconducting nanowire single photon detector, is optically coupled to the heralding waveguide path 1113 and can produce an electrical signal (e.g. a current pulse, also referred to as a photon heralding signal) in response to the detection of the signal photon 1104. Because the signal photon 1104 and idler photon 1106 were generated nearly simultaneously as a pair, the electrical signal generated by the photon detector 1107 signals (i.e., “heralds”) the presence of the idler photon 1106 in the switched output waveguide path 1115. The heralding signal is often a small amplitude current signal, e.g., microamps or less, and can be provided to the superconducting amplifier circuit 1109 where it is amplified to a larger output signal that can be used to more effectively drive any downstream electronic and/or photonic circuits. Referring momentarily to the
In light of these principles and embodiments, we now turn to certain additional embodiments.
In accordance with some embodiments, a transistor (e.g., transistor 100) includes: (1) a first wire including a semiconducting component (e.g., semiconductor layer 102) configured to operate in an on state at temperatures above a semiconducting threshold temperature (e.g., TC 208); and (2) a second wire including a superconducting component (e.g., superconducting layer 106) configured to operate in a superconducting state while: (a) a temperature of the superconducting component is below a superconducting threshold temperature (e.g., TC 206); and (b) an input current supplied to the superconducting component is below a current threshold.
In some embodiments, the semiconducting component is located adjacent to the superconducting component. For example,
In some embodiments, in response to the input current exceeding the current threshold (e.g., current 414 in
In some embodiments, the transistor is configured to operate in an off state while the semiconducting component is maintained at a temperature below the semiconducting threshold temperature. For example, while the semiconducting component is below the semiconducting threshold temperature, the semiconducting component has no current flow as illustrated in
In some embodiments, the transistor is configured to operate in an on state while the semiconducting component is at a temperature above the semiconducting threshold temperature. For example, while the semiconducting component is at a temperature above the semiconducting threshold temperature, the semiconducting component allows current to flow from the source of the transistor to the drain of the transistor as illustrated in
In some embodiments, the superconducting component is a superconducting wire on a first layer, the semiconducting component is a semiconducting wire on a second layer, and an electrically-insulating layer separates the first layer from the second layer. In some embodiments, the superconducting wire is oriented perpendicular to the semiconducting wire (e.g.,
In some embodiments, the superconducting component is a gate of the transistor and the semiconducting component is a source and drain of the transistor. In some embodiments, operating in an on state includes enabling current flow from the source to the drain.
In some embodiments, the superconducting threshold temperature is adjacent to the semiconducting threshold temperature. In some embodiments, the superconducting threshold temperature is below the semiconducting threshold temperature. In some embodiments, the semiconducting threshold temperature is between 5 and 10 Kelvin. In some embodiments, the superconducting threshold temperature is between 10 and 11 Kelvin.
In some embodiments, the superconducting component is a superconducting wire. In some embodiments, the wire is composed of niobium or a niobium alloy.
In some embodiments, the superconducting wire has a constriction (e.g., constriction 301) at a location corresponding to (e.g., adjacent to) the semiconducting component. In some embodiments, the constriction is a region of the superconducting wire with a notch. In some embodiments, the constriction is a region of the superconducting wire with a smaller width than neighboring regions of the wire.
In some embodiments, the superconducting component is configured to generate heat at a location corresponding to (e.g., adjacent to) the semiconducting component during a transition from the superconducting state to a non-superconducting state. In some embodiments, the location corresponding to the semiconducting component is a location closest to the semiconducting component. In some embodiments, the location corresponding to the semiconducting component is a location where the semiconducting component crosses (e.g., crosses over or under) the superconducting component. In some embodiments, the heat generated is sufficient to increase the temperature of the superconducting component by between 3 Kelvin and 10 Kelvin.
In some embodiments, the superconducting component is electrically isolated from the superconducting component. For example, the superconductor layer 106 in
In some embodiments, the first wire has a first region (e.g., region 306) corresponding to (e.g., adjacent to) the superconducting component and secondary regions neighboring the first region (e.g., regions 305 and 307). In some embodiments, the first region includes the semiconducting component. In some embodiments, the semiconducting component includes the first region.
In some embodiments, the first region is configured to operate in the on state at temperatures above the semiconducting threshold temperature and the secondary regions is configured to operate in the on state at temperatures above a second semiconducting threshold temperature, the second semiconducting threshold temperature being below the semiconducting threshold temperature. In some embodiments, the secondary regions and the first region are made of a same semiconductor material (e.g., silicon or germanium). In some embodiments, the secondary regions have a higher doping concentration than the first region and the higher doping concentration lowers the threshold temperature. In some embodiments, the secondary regions have a metal coating and the first region does not.
In some embodiments, the first region is narrower than the secondary regions (e.g., as illustrated in
In some embodiments, the first wire is perpendicular to the second wire. In some embodiments, the first wire is parallel to the second wire. In some embodiments, the first wire is at a non-perpendicular, non-parallel orientation with respect to the second wire.
In accordance with some embodiments, a transistor includes: (1) a superconducting wire on a first layer (e.g., superconductor layer 106); (2) a semiconducting wire on a second layer (e.g., semiconductor layer 102), the semiconducting wire configured to transfer current from a source of the transistor to a drain of the transistor; and (3) an electrically-insulating layer (e.g., insulating layer 104) isolating the first layer from the second layer.
In some embodiments, the first layer is located above the electrically-insulating layer and the electrically insulating layer is located above the second layer. In some embodiments, the second layer is located above the electrically-insulating layer, and the electrically-insulating layer is located above the first layer. In some embodiments, the electrically-insulating layer (e.g., insulating layer 104) is thermally conductive. For example, heat generated by the superconducting wire is transferred through the electrically insulating layer to increase a temperature of the semiconducting wire.
In accordance with some embodiments, a method for fabricating a superconductor-based transistor includes: (1) providing a superconducting wire (e.g., superconductor layer 106); (2) depositing an electrically insulating layer over the superconducting wire (e.g., insulating layer 104); and (3) forming a semiconducting wire (e.g., semiconductor layer 102) on the electrically-insulating layer.
In some embodiments, the electrically insulating layer is composed of AlN. In some embodiments, the superconducting wire is composed of niobium-germanium. In some embodiments, the method includes: (1) providing a semiconducting wire; (2) depositing an electrically insulating layer over the semiconducting wire; and (3) generating (e.g., forming) a superconducting wire on the electrically insulating layer.
In some embodiments, providing the superconducting wire includes: (1) depositing a layer of superconducting material on a substrate; and (2) removing one or more portions of the layer of superconducting material to define the superconducting wire.
In accordance with some embodiments, a method for fabricating a transistor includes: (1) providing a semiconducting wire; (2) depositing an electrically-insulating layer over the semiconducting wire; and (3) forming a superconducting wire on the electrically insulating layer.
In accordance with some embodiments, a photodetector device includes a superconducting wire (e.g., superconducting wire 516,
The superconducting wire (e.g., superconducting wire 516,
In some embodiments, the device further includes one or more current sources coupled to the second wire and configured to supply to the superconducting component a first current that is below the current threshold. For example, as shown in
In some embodiments, the device further includes one or more current sources coupled to the first wire and configured to supply a second current through the semiconducting component.
In some embodiments, the device further includes one or more voltage sources (e.g., voltage source 518,
In some embodiments, in response to receiving light of a first intensity at the superconducting wire, the superconducting component transitions to a non-superconducting state and generates the heat sufficient to increase the temperature of the semiconducting component above the semiconducting threshold temperature. For example, as shown in
In some embodiments, the superconducting component is a gate of the transistor and the semiconducting component is a source and drain of the transistor (e.g., the electrical signal, such as electrical current, applied to the superconducting component controls the current flowing through the semiconducting component).
In some embodiments, the superconducting threshold temperature is adjacent to the semiconducting threshold temperature (e.g., see
In some embodiments, the superconducting component is a superconducting wire. In some embodiments, the superconducting component consists of a superconducting wire. In some embodiments, the superconducting wire has a constriction at a location adjacent to the semiconducting component (e.g.,
In some embodiments, the superconducting component is configured to generate heat at a location adjacent to the semiconducting component during a transition from the superconducting state to a non-superconducting state. In some embodiments, the superconducting component is configured to generate heat at the location adjacent to the semiconducting component while the superconducting component remains in the non-superconducting state.
In some embodiments, the superconducting component is electrically isolated from the superconducting component (e.g., an electrical current flowing through the superconducting component is separate from an electrical current flowing through the superconducting component). In some embodiments, the semiconducting component is composed of germanium.
In some embodiments, the first wire has a first region adjacent to the superconducting component and secondary regions neighboring the first region.
In some embodiments, the first region is configured to operate in the “on” state at temperatures above the semiconducting threshold temperature and the secondary regions is configured to operate in the “on” state at temperatures above a second semiconducting threshold temperature, the second semiconducting threshold temperature being below the semiconducting threshold temperature.
In some embodiments, the first region is narrower than the secondary regions (e.g.,
In accordance with some embodiments, a photodetector device includes a first superconducting wire and a transistor. The transistor includes a second superconducting wire on a first layer; a semiconducting wire on a second layer, the semiconducting wire configured to transfer current from a source of the transistor to a drain of the transistor; and an electrically insulating layer isolating the first layer from the second layer (e.g.,
In accordance with some embodiments, a transistor (e.g., transistor 100) includes: (1) a first wire including a semiconducting component (e.g., semiconductor layer 102) configured to operate in an on state at temperatures above a semiconducting threshold temperature (e.g., TC 208); and (2) a second wire including a superconducting component (e.g., superconducting layer 106). In some embodiments, the superconducting component is configured to operate in a superconducting state while: (a) a temperature of the superconducting component is below a superconducting threshold temperature (e.g., TC 206); and (b) a first input current (e.g., current 604,
In some embodiments, the superconducting component is a superconducting wire on a first layer, the semiconducting component is a semiconducting wire on a second layer, and an insulating layer separates the first layer from the second layer (e.g.,
In some embodiments, the semiconductor component is a gate of the transistor and the superconducting component is a source and drain of the transistor. In some embodiments, operating in an on state includes enabling current flow from the source to the drain.
In some embodiments, the superconducting component is a superconducting wire. In some embodiments, the wire is composed of niobium or a niobium alloy.
In some embodiments, the superconducting wire has a constriction (e.g., constriction 301,
In some embodiments, the transistor is configured to operate in a second mode, where, in the second mode, in response to the first input current (e.g., current 414,
In some embodiments, in the second mode, the superconducting component is configured to generate heat at a location adjacent to the semiconducting component during a transition from the superconducting state to a non-superconducting state (e.g., generate heat as illustrated in
In some embodiments, in the second mode, the superconducting component is a gate of the transistor and the semiconducting component is a source and drain of the transistor.
In some embodiments, the superconducting component is electrically isolated from the semiconducting component. In some embodiments, the superconducting component is separated from the semiconducting component by an insulating layer (e.g., AlN, SiN, silicon oxide, etc.). For example, the superconductor layer 106 in
In some embodiments, the semiconducting component is composed of germanium. In some embodiments, the semiconducting component is composed of silicon.
In some embodiments, the semiconducting component has a first region (e.g., region 306) corresponding to (e.g., adjacent to) the superconducting component and secondary regions neighboring the first region (e.g., regions 305 and 307). In some embodiments, the first region is configured to operate in the on state at temperatures above the semiconducting threshold temperature and the secondary regions are configured to operate in the on state at temperatures above a second semiconducting threshold temperature, the second semiconducting threshold temperature being below the semiconducting threshold temperature. In some embodiments, the secondary regions and the first region are made of a same semiconductor material (e.g., silicon or germanium). In some embodiments, the secondary regions have a higher doping concentration than the first region and the higher doping concentration lowers the threshold temperature. In some embodiments, the secondary regions have a metal coating and the first region does not. In some embodiments, the first region is narrower than the secondary regions.
In accordance with some embodiments, a transistor includes: (1) a first wire including a semiconducting component (e.g., semiconductor component 304) configured to operate in an on state at temperatures above a semiconducting threshold temperature (e.g., 40 Kelvin); and (2) a second wire (e.g., conductor 702) located adjacent to the semiconducting component. In some embodiments: (a) in response to an input current (e.g., current 704), the second wire is configured to generate heat (e.g., heat 708) sufficient to increase a temperature of the semiconducting component above the semiconducting threshold temperature; (b) the transistor is configured to operate in an off state while the semiconducting component is maintained at a temperature below the semiconducting threshold temperature (e.g.,
In some embodiments, the second wire is a gate of the transistor and the semiconducting component is a source and drain of the transistor. In some embodiments, operating in an on state includes enabling current flow from the source to the drain (e.g., current 706 shown in
In some embodiments, the second wire is a superconducting component maintained in a non-superconducting state. In some embodiments, the second wire is composed of niobium or a niobium alloy.
In some embodiments, the second wire has a constriction at a location adjacent to (e.g., corresponding to) the semiconducting component (e.g., as shown in
In some embodiments, the second wire is electrically isolated from the superconducting component. In some embodiments, the superconducting component is separated from the semiconducting component by an insulating layer (e.g., AlN, SiN, silicon oxide, etc.). In some embodiments, the semiconducting component is composed of Germanium and/or Silicon. In some embodiments, the insulating layer is electrically insulating and thermally conductive.
It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first current could be termed a second current, and, similarly, a second current could be termed a first current, without departing from the scope of the various described embodiments. The first current and the second current are both currents, but they are not the same condition unless explicitly stated as such.
The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting” or “in accordance with a determination that,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event]” or “in accordance with a determination that [a stated condition or event] is detected,” depending on the context.
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen in order to best explain the principles underlying the claims and their practical applications, to thereby enable others skilled in the art to best use the embodiments with various modifications as are suited to the particular uses contemplated.
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